In laundry detergents, certain polymers are utilized as soil detachment-promoting additives, which can assist fabric cleaning in addition to surfactants. These polymers may be suitable for use in the laundry liquor as dispersants of soil pigments such as clay minerals or soot, and/or as additives which prevent the reattachment of soil to the fabric being laundered. However, these polymeric dispersants may be ineffective in the removal of hydrophobic soil from textiles, particularly when they are utilized under low temperature washing conditions.
Amphiphilic graft copolymers described in US Patent Applications No. 2009/0005288A1 and 2009/0005287A1 are particularly suited for the removal of hydrophobic soil from fabric in the wash liquor. Consequently, it would be very desirable to provide a granular laundry detergent composition comprising such polymers.
Because such amphiphilic graph copolymers are highly viscous and difficult to handle, they have been in the past provided as polymeric solutions, which is either mixed with surfactant slurry to form blown powders through a spray-drying process or is directly sprayed onto already-formed surfactant particles to form a coating layer thereover.
However, when the amphiphilic graph copolymers form a part of the surfactant granules, it is very difficult to freely adjust the levels of such copolymers in the finished products, without affecting the surfactant activity of the finished products. It is therefore desirable to form granules or particles that contain only the amphiphilic graph copolymers, with little or no surfactant therein.
US2011/0152161 discloses surfactant-free agglomerates containing about 23% amphiphilic graft copolymers (“AGPs”) in combination with about 48.5% sodium carbonate and 20% zeolite. One of the biggest drawbacks to use zeolite in granular laundry detergents is cost. Therefore, such a high level of zeolite in the agglomerates disclosed by US2011/0152161 will drive up the overall manufacturing costs significantly, and will not meet the consumer demands for low-cost detergents.
Zeolite is a porous material with very high active surface area and correspondingly a large liquid loading capacity. Without the structural support of zeolite in the agglomerates, it is questionable whether solid agglomerates can be formed at all, e.g., the resulting mixture may be a viscous paste or slurry. Even if solid agglomerates are formed, it is likely that a significant amount of such agglomerates will be “oversized” particles, i.e., having particle sizes that are above a standard particle size range, e.g., from about 150 microns to about 1200 microns or preferably from about 250 microns to about 1000 microns. For the granular or powder-type laundry detergent products, it is important to ensure that all of the granules or particles in such products are within the standard particle size range, because granular or powder products with a more uniform particle size distribution have a more refined, high-quality appearance. Further, when the granules or particles are more similar in particle sizes, they are less likely to segregate during shipping and handling. Therefore, it is a typical practice in agglomeration process to remove either undersized particles (i.e., fines with particle sizes smaller than 150 or 250 microns) or oversized particles (i.e., overs with particle sizes larger than 1000 or 1200 microns). Such removed fines or overs will be recycled, processed (e.g., by grinding the oversized particles down to smaller-sized particles) and added back into the manufacturing process stream. For a specific manufacturing process, the higher amount of fines or overs is generated, the more energy will be consumed and the higher the cost will be in order to turn a unit amount of raw materials into finished products. Corresponding, a person ordinarily skilled in the art will be reluctant to reduce the amount of zeolite used in the agglomeration process, for fear of significantly increasing the amount of oversized particles generated and driving up the processing cost.
Further, the agglomerates formed with less zeolite may have a higher tendency to “cake” and a poorer flowability, which will render consumer use of the finished products more difficult and inconvenient. Therefore, a person ordinarily skilled in the art will be reluctant to reduce the amount of zeolite used in the agglomeration process, for fear of
There is currently a need to provide surfactant-free particles containing the amphiphilic graft copolymers, which can be formed by an agglomeration process at relatively low cost, i.e., without using zeolite as a builder, but at the same time without generating a significant higher amount of oversized particles and without compromising flowability of the agglomerates so formed.